Generally, in a vehicle having an internal combustion engine mounted thereon, a catalytic device is provided to purify exhaust gas. Since this catalytic device does not produce any effect unless the temperature rises to some extent, the catalytic device is arranged close to the internal combustion engine such that the temperature rises immediately.
The purification effect is not perfect, however, immediately after startup of the internal combustion engine, that is, when the catalytic device has not yet been warmed. In addition, in a hybrid vehicle capable of running using only a motor, the internal combustion engine is operated as necessary. The catalytic device, however, is not always warmed by exhaust gas at the time of startup of the internal combustion engine. Therefore, warming the catalytic device in advance using electric power before startup of the internal combustion engine is under consideration. Such a catalytic device is called “Electrical Heated Catalyst” (hereinafter also referred to as “EHC”). The EHC generates heat by passing current through the catalytic device itself. Japanese Patent Laying-Open No. 2010-223159 (PTL 1) discloses a technique of preventing leak at the time of passing current through an EHC and suppressing deterioration in emission in a vehicle having the EHC mounted thereon. According to this technique, in a plug-in hybrid vehicle, an ECU first executes low-voltage driving of restraining driving voltage to 50 V when requesting passage of the current through the EHC, and detects the existence of occurrence of the leak caused by dew condensation of condensate in the EHC based on a resistance value of the EHC. As a result, when it is determined that the leak is occurring, passage of the current through the EHC is prohibited. On the other hand, when it is determined that the leak is not occurring, the driving voltage is boosted to 200 V in ordinary driving, and catalytic warming-up by the EHC is executed.